Biopolymer foams as filters for smoking articles

ABSTRACT

A process for preparing a filter plug for a smoking article, such as a cigarette, includes: (a) freeze-drying a solution of a biopolymer to form a structure; and (b) cutting the structure to a predetermined dimension, to thereby prepare a filter plug for a smoking article. Another process for preparing a filter plug for a smoking article, such as a cigarette, includes: (a) extruding a mixture of a foaming agent and a biopolymer comprising a protein to form a structure; and (b) cutting the structure to a predetermined dimension, to thereby form a filter plug for a smoking article.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.13/072,166, filed on Mar. 25, 2011, which claims priority under 35U.S.C. § 119(e) to U.S. provisional Application No. 61/318,265, filed onMar. 26, 2010, the entire content of which is incorporated herein byreference.

BACKGROUND

Cellulose acetate (CA) fibers are often used in producing tobaccosmoking filter plugs for smoking articles such as cigarettes. In aconventional process of manufacturing a cigarette filter plug, celluloseacetate fibers are crimped, entangled and bonded to each other bybinders such as triacetin (i.e., glycerin triacetate).

After a smoking article is consumed, it is discarded. Typically,cellulose acetate fibers contained in the smoking article degrade slowerthan tobacco and/or the paper parts of the cigarette article, therebycontributing litter to the environment. To reduce the environmentalburden of discarded filtered smoking articles, there is interest indeveloping cigarette filter plugs having an improved degradation rate.

SUMMARY

According to a first embodiment, a process for preparing a filter plugfor a smoking article, such as a cigarette, comprises: (a) freeze-dryinga solution of a biopolymer to form a structure; and (b) cutting thestructure to a predetermined dimension, to thereby form a filter plugfor smoking articles.

According to a second embodiment, a process for preparing a filter plugfor a smoking article, such as a cigarette, comprises: (a) extruding amixture of a foaming agent and a biopolymer comprising a protein to forma structure; and (b) cutting the structure to a predetermined dimension,to thereby form a filter plug for smoking articles.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a digital image showing agar foam rods prepared by afreeze-drying process.

FIG. 2 is an image of a bench top freeze-dryer.

DETAILED DESCRIPTION

Processes for preparing foams from biopolymers, which are useful asfilters for smoking articles such as cigarettes are described herein.

The term “biopolymer,” as used herein, is understood by those skilled inthe art and generally refers to a special class of polymers produced byliving organisms and are biodegradable. A biopolymer may include anypolymer (a long repeating chain of atoms) found in nature.

The term “foam,” as used herein, denotes a network of communicatingmicro-compartments with biopolymer molecules and/or filamentsinterspersed throughout its walls.

The term “smoking article,” as used herein, denotes an articlecontaining a charge of smoking composition formed into a rod or column,and which may optionally be surrounded by a wrapper, which helps to holdthe shape of the rod and contain the smoking composition within thesmoking article. The rod of smoking material, or the wrapper therefor,or both can be burned or heated during use of the smoking article undersmoking conditions. A smoking article may also contain one or morefilter plugs, which can function to remove targeted constituents from,and provide aesthetically pleasing qualities to, the smoke. The term“smoking article” is intended to include cigarettes, which include bothtraditional cigarettes and non-traditional cigarettes.

The term “traditional cigarette,” as used herein, denotes a cigarettethat can be smoked by lighting an end of a wrapped rod or column of asmoking composition and drawing air predominantly through the lit end bysuction at a mouthpiece end of the cigarette. Traditional cigarettesoften contain a filter element to remove or reduce targeted constituentsin the smoke. A filter element typically composed of one or more piecesof filter material wrapped by a wrapper known as a plug wrap, which cantypically be attached to one end of the rod of shredded smokingcomposition (e.g., tobacco, also referred to as a “tobacco rod”) bymeans of a wrapping or tipping material.

In addition, non-traditional cigarettes include, but are not limited to,cigarettes for electrical smoking systems as described incommonly-assigned U.S. Pat. Nos. 6,026,820; 5,692,526; 5,692,525;5,666,976; and 5,499,636. Other non-traditional cigarettes include thosehaving a fuel element in the tobacco rod as described in U.S. Pat. No.4,966,171.

As used herein, the term “flavorant” denotes one or more compounds thatare perceived by taste receptors or olfactory sensory cells of aconsumer, but includes compounds that are perceived by additional sensesas well. Suitable flavorants include cycloalkyl alcohols and arylalcohols, such as menthol, thymol, and eugenol.

In an embodiment, a filter plug for a smoking article comprises abiopolymer foam produced by a freeze-drying process or a blown-foamextrusion process. In a preferred embodiment, the biopolymer comprises anatural biopolymer. Examples of suitable biopolymers include, but arenot limited to, polysaccharides and proteins. Specifically, thebiopolymer may contain one or more of carrageenan, agar, guar, pectinsuch as tobacco-sourced pectin, starch, alginate, chitosan, gelatin,wheat protein, rice protein, pea protein, soy protein, fish protein, andthe like. These biopolymers may be used individually or in combinationthereof.

Freeze-drying (also known as lyophilization) is a dehydration processcomprising: (a) freezing a solution of a material in a suitable solvent,e. g., water; (b) then reducing the surrounding pressure to allow thefrozen water or other suitable solvent in the material to sublimedirectly from the solid phase into the gas phrase; and (c) heating theresulting material. The eutectic temperature, that is the minimumfreezing point for the entire volume of material being frozen, varieswith the concentration of the material in solution. Thus, thefreeze-drying conditions, such as temperature and period of time, willvary as a function of the material concentration in solution.

The biopolymer foam can be formed in any dimension and/or shape, eitherregular or irregular, e. g., by conducting freeze-drying in a containerhaving the desired dimension and/or shape, as long it has a dimensionlarger than a filter plug for a smoking article.

In one embodiment, the freeze-drying is carried out in a cylindricalcontainer, such as a tube. The cylindrical container preferably has adiameter of about 0.8 cm, which is the same as that of a filter for asmoking article, to thereby produce a biopolymer foam rod.

Various solvents, e. g., water, alcohol, and acetone, isopropyl alcohol,propylene glycol, etc., may be used to prepare the biopolymer solution.In an embodiment, the biopolymer can be dissolved in water to obtain anaqueous solution of biopolymer. The concentration of biopolymer in theaqueous solution preferably is the range from about 0.1% to about 50%,and more preferably, from about 0.5% to about 5%, based on the totalweight of the solution. However, the concentration of the biopolymer inthe solution can be in the range from about 5% to about 10%, from about10% to about 20%, from about 20% to about 30%, from about 30% to about40%, or from about 40% to about 50%, based on the total weight of thesolution.

In a particular embodiment with a bench top freeze-dryer, such as thatshown in FIG. 2, a 2% aqueous solution of agar in a plastic tube havinga diameter of about 0.8 cm can be placed in a flask. The flask can thenbe connected to vacuum and left overnight. FIG. 1 is a digital imageshowing the thus-prepared agar foam rods.

In addition, when a larger freeze-dryer is involved, a temperatureprogram may be used. For example, an aqueous solution of a biopolymermay be freeze dried at a temperature ranging from about −40° C. to about−100° C. and under a pressure ranging from about 0.01 mbar to about 0.1mbar. This freeze-drying may substantially complete in about 1 hour toabout 10 hours.

In an embodiment, freeze-drying may be conducted by: (a) cooling a 2%aqueous solution of agar in a plastic tube having a diameter of about0.8 cm to about −80° C. and maintaining this temperature for about 3hours; (b) applying a vacuum of about 0.02 mbar; and (c) raising thetemperature to about 20° C. and maintaining this temperature for 24hours.

This freezing-drying-heating cycle may optionally be repeated one ormore times. The content of water or other suitable solvent in the finalfreeze-dried product is preferably in the range of about 1% to about 5%,based on the total weight of the final product.

The blown-foam extrusion process may be performed by various methods.For example, a mixture containing the biopolymer and optionally afoaming agent is passed into or through a heated mold. The foaming agentis not particularly limited. Examples of suitable foaming agent include,but are not limited to, air, N₂, CO₂, water vapor, sodium bicarbonate,sodium bicarbonate/citric acid, pentane, and cyclopentane. For example,the foaming agent can be used in an amount ranging from about 5% toabout 20%, based on the weight of biopolymer.

Alternatively, a mixture containing the biopolymer and optionally afoaming agent is passed into or through a heated mold (extruded) alongwith an inert gas, such as CO₂ and N₂. The inert gas may be introducedat a rate of about 15%.

The temperature of the mold may vary depending on various factors, e.g., the types of biopolymer and solvent utilized. For example, thetemperature of the mold can be set at about 100° C. to about 250° C.,and preferably, from about 150° C. to about 180° C.

The biopolymer foam can be formed by a blown-foam extrusion process inany dimension and/or shape, either regular or irregular, by employing amold of the desired cross-section or diameter, as long it has adimension larger than a filter plug for a smoking article.

In one embodiment, the mixture containing the biopolymer is passed intoor through a mold having a diameter of about 0.8 cm, which is the sameas that of a filter for a smoking article, to thereby produce abiopolymer foam rod.

The resulting biopolymer foam, obtained by either freeze-drying orblown-foam extrusion, preferably has an average pore size ranging fromabout 0.04 millimeters to about 0.20 millimeters, thereby allowingpassage of smoke components during smoking and further improvingbiodegradability upon disposal.

Moreover, the biopolymer foam can be engineered with desired watersolubility, so as to delay premature degradation thereof during theuses. The solubility of the biopolymer foam may be manipulated byvarious methods, e. g., by incorporating one or more water insolublecopolymers, such as cellulose acetate. For example, a water insolublecopolymer may be incorporated in an amount ranging from about 0.1% toabout 10%, based on the weight of the biopolymer.

Other properties of the biopolymer foams, e. g., hardness andelasticity, can also be controlled by using various cross-linking agentsor mixed biopolymer systems, or the use of specific types of biopolymersor plasticizers. These properties of the biopolymer foams can controlthe permeability and release characteristics thereof and thus may beadjusted according to end uses.

Other additives, such as calcium carbonate or other salts, and clay, mayalso be added to the biopolymer foams in an amount which does notadversely affect the characteristics of the biopolymer foams.

The biopolymer may be cross-linked to produce a cross-linked biopolymerfoam. The cross-linking can be performed in presence of a cross-linkingagent and/or by radiation, e. g., ultraviolet radiation at a wavelengthof about 254 nm, either before, during and/or after the freeze-drying orblown-foam extrusion procedure. Cross-linking can be performed prior to,during or subsequent to the freeze-drying.

A cross-linking agent is a compound which contains the appropriatefunctional groups to react with the free functional groups, e.g.,between polymer molecules. The cross-linking agents are not particularlylimited as long as they are capable of cross-linking the biopolymer.

Examples of suitable cross-linking agents include, but are not limitedto, (a) polyfunctional acids (two or more carboxylic groups); (b) acidchlorides of polyfunctional carboxylic acids (e.g., adipoyl chloride);(c) acid anhydrides of polyfunctional carboxylic acids; (d) carbonylchloride; (e) aldehydes and dialdehydes; (f) (NH₄)₂HPO₄; (g) ketenes;(h) lactones; (i) azides and diazides; (j) aldehydic and keto sugars(glucose, fructose, dextrose, etc.); (k) polybasic inorganic acids andsalts thereof; and (l) amides. Bi- or trivalent metal ion salts can alsobe used as cross-linking agents. For example, cross-linking agents maycontain alkaline salts and particularly, salts of alkaline earth metals.These cross-linking agents may be used individually or in combinationthereof.

Preferred polyfunctional carboxylic acids include citric, maleic, malic,malonic, ethylenediamine tetracetic, polymannuronic, polygalacturonic,adipic, azelaic, tartaric and succinic acids.

Preferred polybasic inorganic acids include phosphoric, hypophosphorousand sulfuric acids and the ammonium and alkali metal salts thereof.

In one embodiment, the cross-linking agent comprises calcium chloride orcalcium lactate.

The amount of cross-linking agent for preparation of the cross-linkedbiopolymer foam may vary depending on the composition used, inparticular, the biopolymer contained therein. For example, thecross-linking agent can be used in an amount of about 0.2% to about 15%,and preferably, about 2%, based on the amount of the biopolymer.

Further, a mixture of biopolymers may be used to form the biopolymerfoam. In one embodiment, one or more natural biopolymers may be used incombination with one or more synthetic biopolymers to produce a foamwith desired textures. Examples of suitable synthetic biopolymersinclude, but are not limited to, poly(vinyl alcohol), poly(ethyleneglycol) and the like. The ratio of natural biopolymer:syntheticbiopolymer may range from about 0% to about 100%. In an embodiment, thenatural biopolymer:synthetic biopolymer ratio is from about 1% to about20%, from about 20% to about 40%, from about 40% to about 60%, fromabout 60% to about 80%, or from about 80% to about 99%.

Moreover, one or more biopolymers may optionally be used in combinationwith a plasticizer to form a foam. The presence of a plasticizer can, tosome extent, alter foam structures and/or textures. The plasticizer isnot particularly limited. Examples of suitable plasticizers include, butare not limited to, certain tobacco extracts, monobasic, dibasic andtribasic acids such as lactic, malic, tartaric and citric, butyleneglycols, sorbitol, sorbitan, sucrose, oligosaccharides, triglyceridefats and oils, long chain fatty alcohols, linear paraffins, normalparaffins, paraffin waxes, beeswax, candelilla wax, carnauba wax andsugar cane wax. These plasticizers may be used individually or incombination thereof. The plasticizer, when employed, can be contained inan amount ranging from about 0.5 parts (by weight) to about 100 parts,and preferably, about 0.5 parts (by weight) to about 20 parts, per 100parts of the biopolymer.

The biopolymer foams may also be engineered to contain further channels,voids and/or cavities therein, to increase the surface areas thereof.For example, small objects may be included in a solution forfreeze-drying process or a mixture for blown-foam extrusion process, andsubsequently removed after formation of the biopolymer foam.Alternatively or additionally, dies with different cross-section and/orshapes may be employed in a blown-foam extrusion process to produce thebiopolymer foam.

The resulting biopolymer foam can then be cut into a dimension and/orshape which is suitable for use in a filter of smoking articles. In oneembodiment, a biopolymer foam rod can be cut into a predeterminedlength, thereby producing one or more filter plugs for smoking articles.In another embodiment, the biopolymer foam is in the form of a sheet,the thickness of which is the same as the length of the desired filterplug. Such biopolymer foam can be stamped with a tube mold having adesired diameter to thereby form a filter plug.

The biopolymer foams can have a high surface area plateletmicrostructure which is rich in functional bonding sites and can serveas a support for active surface chemistry or modified for selectivefiltration.

Moreover, the foam structure can physically capture and include otherfibrous, ground or granular materials such as cellulose or celluloseacetate for chemical or taste compatibility. In addition, sorbents, suchas active carbon, may be incorporated into the biopolymer foams in afilter for smoking articles in an appropriate amount, to remove targetedcomponents from smoke. The sorbent can be incorporated in the foamstructure prior to, during or subsequent to the freeze-drying.

Further, the biopolymer foams can be flavored or impregnated with aromasand function for flavor capture/release as desired. For example, aflavorant, in gaseous, solid or liquid form, can be added to abiopolymer solution prior to or during the formation of the biopolymerfoam. Alternatively, a flavorant in solid or liquid form, e. g., bysoaking, spraying and dropping, to may be incorporated to the formedbiopolymer foam.

In one embodiment, a flavorant is incorporated into the biopolymer foamsubsequent to the formation thereof, as such the flavorant is adsorbedor absorbed merely on surfaces of the foam. In addition, byincorporation of the flavorant subsequent to the foam formation,potential loss of the flavorant during the foam formation can be avoidedor reduced. The amount of flavorant incorporated may vary depending onthe type of the flavorant and desired experiences.

The flavorants which can be incorporated in the biopolymer foam are notparticularly limited. Examples of suitable flavorants include, but arenot limited to, menthol, peppermint, spearmint, wintergreen, cinnamon,chocolate, vanillin, licorice, clove, anise, sandalwood, geranium, roseoil, vanilla, lemon oil, cassia, fennel, ginger, ethyl acetate, isoamylacetate, propyl isobutyrate, isobutyl butyrate, ethyl butyrate, ethylvalerate, benzyl formate, limonene, cymene, pinene, linalool, geraniol,citronellol, citral, peppermint oil, orange oil, coriander oil, borneol,fruit extract, tobacco flavor, e.g., tobacco extract, and the like.These flavorants may be used individually or in combination thereof. Apreferred flavorant comprises menthol.

The filter plug described above can be incorporated in cigarettes. Thetobaccos used in these cigarettes are not particularly limited. Examplesof suitable types of tobacco materials include, but are not limited to,flue-cured tobacco, Burley tobacco, Maryland tobacco, Oriental tobacco,rare tobacco, specialty tobacco, reconstituted tobacco, agglomeratedtobacco fines, blends thereof, and the like. Preferably, the tobaccomaterial is pasteurized. Some or all of the tobacco material may befermented.

Further, the tobacco material may be provided in any suitable form.Examples of suitable forms include shreds and/or particles of tobaccolamina, processed tobacco materials, such as volume expanded or puffedtobacco, or ground tobacco, processed tobacco stems, such as cut-rolledor cut-puffed stems, reconstituted tobacco materials, blends thereof,and the like. Genetically modified tobacco may also be used.

The biopolymer foam, when used in filters for smoking articles, such ascigarettes, can have accelerated biodegradation rates in comparison withcellulose acetate filters.

A specific non-limiting example is provided below.

EXAMPLE

Preparation of Agar Foam Rods as Cigarette Filters

A mixture of agar (2.0 g) and de-ionized (DI) water (98 g) is heated to100° C. until agar is completely dissolved and a clear solution isformed. Plastic tubing of appropriate cigarette filter diameter isfilled with the hot agar solution and then cooled down to roomtemperature. The resulting gel is frozen at −80° C. for 3 hours and thenfreeze-dried for 24 hours at a pressure of 0.02 mbar. The freeze-driedagar foam is warmed to room temperature. The foam rods are removed fromthe plastic tubing and cut to appropriate length for use as cigarettefilters.

While the foregoing has been described in detail with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications may be made, and equivalentsthereof employed, without departing from the scope of the claims.

All of the above-mentioned references are herein incorporated byreference in their entirety to the same extent as if each individualreference was specifically and individually indicated to be incorporatedherein by reference in its entirety.

We claim:
 1. A process for preparing a filter plug for a smokingarticle, comprising: (a) extruding a mixture of a foaming agent and abiopolymer to form a biopolymer foam rod structure; and (b) cutting thestructure to a predetermined dimension, to thereby form a filter plugfor a smoking article, wherein the biopolymer is at least one selectedfrom the group consisting of carrageenan, agar, guar, pectin, alginateand chitosan, and the process further comprises cross-linking thebiopolymer, prior to, during or subsequent to the extruding.
 2. Theprocess of claim 1, wherein the biopolymer further comprises a syntheticbiopolymer.
 3. The process of claim 2, wherein the synthetic biopolymeris at least one selected from the group consisting of poly(vinylalcohol) and poly(ethylene glycol).
 4. A process for preparing a filterplug for a smoking article, comprising: (a) extruding a mixture of afoaming agent and a biopolymer to form a biopolymer foam rod structure;and (b) cutting the structure to a predetermined dimension, to therebyform a filter plug for a smoking article, wherein the biopolymer is atleast one selected from the group consisting of wheat protein, riceprotein, pea protein, soy protein, and fish protein, and the processfurther comprises cross-linking the biopolymer, prior to, during orsubsequent to the extruding.
 5. The process of claim 1, wherein thefoaming agent is contained in an amount ranging from about 5% to about20%, based on the weight of the biopolymer.
 6. The process of claim 1,wherein the extruding (a) is carried out at a temperature ranging fromabout 100° C. to about 250° C.
 7. The process of claim 1, wherein themixture further comprises: (i) a plasticizer and (ii) a water insolublecopolymer.
 8. The process of claim 7, wherein: (i) the plasticizer iscontained in an amount ranging from about 0.5 parts to about 100 parts,by weight, per 100 parts of the biopolymer and (ii) the water insolublecopolymer is contained in an amount ranging from about 0.1% to about10%, based on the weight of the biopolymer.
 9. The process of claim 1,further comprising incorporating a flavorant compound and/or a sorbent,prior to, during or subsequent to the extruding (a).
 10. The process ofclaim 1, wherein the mixture includes at least one cross-linking agentin an amount of about 1% to about 15% based on the amount of thebiopolymer.
 11. The process of claim 1, wherein the foaming agentcomprises air, N₂, CO₂, water vapor, sodium bicarbonate, sodiumbicarbonate/citric acid, pentane, or cyclopentane.
 12. The process ofclaim 1, wherein the foaming agent comprises CO₂, sodium bicarbonate,sodium bicarbonate/citric acid, pentane, or cyclopentane.
 13. A processfor preparing a filter plug for a smoking article, comprising: (a)extruding a mixture of a foaming agent and a biopolymer to form astructure; and (b) cutting the structure to a predetermined dimension,to thereby form a filter plug for a smoking article, wherein thebiopolymer comprises carrageenan, agar, guar, pectin, alginate orchitosan, and radiating the biopolymer to produce a cross-linkedbiopolymer.
 14. The process of claim 13, comprising radiating thebiopolymer at a wavelength of about 254 nm.
 15. The process of claim 4,wherein the biopolymer further comprises a synthetic biopolymer.
 16. Theprocess of claim 15, wherein the synthetic biopolymer is at least oneselected from the group consisting of poly(vinyl alcohol) andpoly(ethylene glycol).
 17. The process of claim 4, wherein the foamingagent comprises air, N₂, CO₂, water vapor, sodium bicarbonate, sodiumbicarbonate/citric acid, pentane, or cyclopentane.
 18. The process ofclaim 4, wherein the foaming agent comprises CO₂, sodium bicarbonate,sodium bicarbonate/citric acid, pentane, or cyclopentane.
 19. A processfor preparing a filter plug for a smoking article, comprising: (a)extruding a mixture of a foaming agent and a biopolymer to form astructure; and (b) cutting the structure to a predetermined dimension,to thereby form a filter plug for a smoking article, wherein thebiopolymer is at least one selected from the group consisting of wheatprotein, rice protein, pea protein, soy protein, and fish protein, andradiating the biopolymer to produce a cross-linked biopolymer.